Blackboard compound



COATING OR PLASTIC.

\106. COMPOSITIONS,

- B LACKBOARD To all whom it ma concern:

Be it known that I, ARTHUR H. WILLIAMS, a citizen ol' the United States, residing at Manchester, in the county of Hillsborough and State of New Hampshire, have invented certain new and useful Improvements in Blackboard m pounds; and I do hereby declare the following to be a full, clear, and exact description of theinvention, such as will enable others skilled in the art to which it appertains to make and use the same.

My invention has reference to an improved mixture for a blackboard or marking surface; and it consists in a blackboard or marking surface composed of certain ingredients, substantially as will be described and then claimed.

One of the constituents of my blackboard composition is Francestown soapstone, which is quarried at Francestown, New Hampshire, and which differs chemically from the ordinary soapstone or tale in that the latter contains no oxide of aluminium (A1 0,) which is contained in Francestown soapstone-to the extent of ten per cent., and also talc has fifteen per cent. more silica (SiOQ than Francestown soapstone, which contains about forty-five per cent. of silica. e I My improved blackboard also comprises cement either Portland or Keene lime- )utt .30; a Black colorin m" atter a'nii'or'dlnary san 'lhe ingredients ust enumerated are com gled in the following proportions: One part ter op parts oi s3 l] ese are t or- Francestown soapstone, qp e part cement one p I part limeu t2, one part black colon n qnatam d 'TE 5 PATENT -OFFICE.

ARTHUR H. WILLIAMS, OF MANCHESTER, NEW HAMPSHIRE.

COMPOUND.

SPECIFICATION forming part of Letters Patent N 0. 392.482, dated November 6, 1888. Application filed May 12, 1888. Serial No. 273,661. (No specimens-l oughly mixed, and to five parts of the mixture ff mi Cross Reference and crayon marks can be easily andcompletely erased. There are no scams or joints and no scaling or wearing off occurs.

Having thus described my improvement in blackboard surfaces or compositions, what I claim as new, and desire to secure by Letters Patent, is

1. A blackboard or marking surface composed of cement lime-m tt black coloringmatter, sand, plaster-of-paris, and a spaptonc containing some ten per 3556. of oxidml'ifi minium and some forty-five per cent of silica, substantially as described.

2. A blackboard or marking surface composedof one part of plaster-of-paris and five parts of a mixture of soapstone containing ten per cent. of oxide of aluminium and some forty-five per cent. of silica, (one part,) cement,

(one part,) lime-putty, (one part,) black coloring-matter, (one part,) and sand, (five parts,)

substantially as described.

In testimony whereof I affix my signature in presence of two witnesses.

ARTHUR H. WILLIAMS.

Witnesses:

O. H. BARTLETT, O. A. WILLIAMS. 

